The disclosed embodiments generally relate to processes and systems for producing alpha olefins and more particularly to a batch process for the production of alpha olefins.
A conventional process for production of comonomer grade hexene-1 from C4 raffinate feed streams is a continuous process that has three stages. First butene-1 is separated from the feed stream in a C4 fractionator. The butene-2 in the fractionator bottoms stream is isomerized to butene-1 and recycled to the fractionator. Second, the butene-1 is sent to an autometathesis reactor to form ethylene and hexene-3. The reactor effluent is sent to a depentanizer to separate hexenes. The products are lights that go overhead, the hexene-3 is a liquid bottoms product, and the C4/C5 products are recycled. Third, the hexene-3 feed is isomerized and the hexene-1 product is separated in a C6 fractionator.
U.S. Pat. No. 6,727,396 (Gartside, April 2004) describes a continuous process for production of hexene-1, combining the isomerization and metathesis steps. Typical metathesis reactions are described in U.S. Pat. No. 3,595,920 (Ellis et al, July 1971). U.S. Pat. No. 4,709,115 (Jung et al, November, 1987) discusses improving the selectivity and conversion of butene-1 and butene-2 to hexene-3 by using catalytic distillation. The removal of the lighter components pushes the reaction equilibrium toward the heavy products. U.S. Pat. No. 5,057,638 (Sweeney, October 1991) discusses a method for production of hexene-1 from butene-1 in which the butene-1 is metathesized to hexene-3. Subsequently, a hydration/dehydration procedure is applied to produce a mixture of n-hexenes containing hexene-1.
Various other processes are known for the processing of C4 olefins. U.S. Pat. No. 6,875,901 (Gartside et al, April 2005) describes olefin isomerization technology used for production of terminal olefins. The process is applied to the production of butene-1 from butene-2. U.S. Pat. No. 6,777,582 (Gartside et al, August 2004), describes butene-1 autometathesis technology, including differences from the conventional metathesis reaction of butene-2 and ethylene to produce propylene.
Closed-loop heat pumps are used in various processes. U.S. Pat. No. 6,589,395 describes a process in which a closed-loop heat pump is included on a general distillation tower. This document describes the use of a heat source and heat sink that can be substituted for the heat pump should the compressor fail. U.S. Pat. Nos. 5,386,075 (Keil et al, January 1995) and No. 4,615,769 (Horigome et al, October 1986) discuss the use of an open-loop heat pump in an ethylbenzene/styrene distillation.
It would be useful to develop a process for producing alpha olefins that has improved efficiency when operated on a small scale.